1. Field of the Invention
The present invention relates to apparatus for placing a false twist in yarn; and more particularly, it relates to a texturizing spindle for imparting a false twist to yarn by parallel rotating discs.
2. Description of the Prior Art
False twist texturizing is a technique which is in itself well known and is widely used, and which basically involves overtwisting a thermoplastic yarn, fixing this deformation, and then untwisting the yarn by the amount that it has been twisted.
It has been known in the art to impart a false twist to a moving yarn by means of a disc, as disclosed in U.S. Pat. No. 1,030,179 to Hilden. It has also been proposed to use this concept in false twist texturizing. For this purpose, friction discs are spaced apart on revolving bosses which are substantially parallel, the discs overlapping from one shaft to another. Illustrative of this arrangement are French Pat. Nos. 1,202,393 and 1,255,922 to Scragg and 1,261,747 to Zavody.
In spindles having three bosses, which are currently the most widely used, it is known to arrange the three revolving bosses, which serve as shafts and carry the discs, in such a way that in a plan view the bosses form the apices of an equilateral triangle. With this arrangement, the yarn to be treated traverses the assembly by following a zig-zag path between the discs which overlap one another.
In order to indroduce the yarn between the discs it is necessary first to disengage the spindle and then either individually to shift one shaft relative to the other two, as taught in French Pat. No. 1,203,072 to Hobourn, or to shift the three shafts equally, as taught in French Pat. Nos. 2,176,826 and 2,225,554 to Kugelfischer or in British Pat. No. 1,379,960 to Scragg. This produces a small rectilinear passage into which the yarn will be fed. Next, the spindle is engaged by bringing the three axles into their working position, with the discs overlapping one another.
Prior art spindles with three bosses, such as that illustrated in FIG. 1, essentially comprise a horizontal platen 1 having bosses 2 mounted perpendicularly thereon, each of which is equipped with a friction disc. The bosses 2 are interconnected and driven synchronously by a ridged belt 4 which passes over a motor pulley 3 mounted on the platen 1. The motor pulley 3 is caused to rotate by the tangential belt 6, with an adjustable pulley 7 regulating the tension of ridged belt 4. The platen 1 slides horizontally on two parallel guides 5.
When it is desired to engage the spindle, placing it in the operating position, it is only necessary to move the platen 1 in the direction of the arrow F1 so as to bring the motor pulley 3 into contact with the tangential belt 6. Pulley 3 is thus caused to rotate and, in turn, drives the bosses 2. To disengage the spindle, platen 1 is shifted in the opposite direction, as shown by the arrow F2, to move the motor pulley 3 away from the belt 6, causing the rotation of the pulley 3, and hence the rotation of the bosses 2, to stop.
Though this conventional assembly is widely used, it nevertheless suffers from the disadvantage of shifting the bosses during the engagement and disengagement operations. In effect, in spite of the rigid fixing of these bosses on the platen, the sliding of this component on guides necessarily requires a certain play in the assembled unit and this play is a source of vibrations which introduce irregularities in the twist and cause premature wear of the bearings. This shifting of the platen is furthermore objectionable because it results in two positions of the yarn.